pure speed:]

Hey how long do should rear case bearings last? Why i ask is because i got like maybe 3 gallons on my os.21tm and the rear bearing is grity like when i turn it and i can see the crank has a slight wobble.

378

My Feedback: (4)

They should last the life of the engine. ESPECIALLY in an OS. I'd check your air filter boot, dirt might be getting in there. If that's not the case, then they rusted up and need to be replaced.

Rendegade

Incorrect. They'll last as long as they last.

If you're using high nitro fuels and aren't using the engine for long periods (and not putting in after run oil) the bearings can rust. After that, they're throwaways.

Take the back plate off the engine if you can, and have a peek at the bearings. IF they look nasty, replace them.

378

My Feedback: (4)

...They should last the life of the engine. If the bearings, in an OS especially but even in a junk engine, are going out after just three gallons, there's something else wrong.

rcdude7

My Feedback: (264)

Three gallons is a lot of running for a 3.5cc engine. Bearings do not last forever, not even close. Most bearings are killed by rust that forms during storage. The conditions in a stored engine favor rust and once the races begin to show pitting they will wear and corrode at a accelerated rate, and get rough quickly as you can see, and feel. Time to replace your bearings. If you don't repace the bearings when needed, the cages can break, releasing metal scrapnel into the rest of the engine and destroying it.

rcdude7

My Feedback: (264)

I don't want to start a @&*%ing contest, buy what you say would only hold true in a perfect world, under perfect conditions, in a engine that is flused with fresh oil between outings. In the real world, 90% of glow engine bearings die of rust long before they actually "wear out".

In a gasoline engine, you would be right, bearings are expected to run until they develop clearances beyond the service limit and do not tend to rust.

378

My Feedback: (4)

I've got an engine on my desk I actually pumped water with.* It's bearings haven't rusted. If they rust in an engine actually in service that engine isn't being cared for properly. The bearings should last the life of the piston and sleeve. No 'ideal world' nonsense about it, if they're well cared for they'll outlast the piston and sleeve. But hey, if you want to treat one of the hardest to replace parts of your engines like they're disposable, then be my guest. Me? I'll stick to running them out of fuel after I'm done and not letting them rust in the first place. I'll try to contain the smugness when they're still serviceable long after the piston and sleeve have worn out.


*Oh, and if you're wondering why I'd do that to an engine, the engine was completely fried and I never had any intention of doing anything more than making a nifty keychain out of the innards and using the block as a paperweight. So I decided to find out how hard it was to hydraulic one. If your curious, the backplate gasket let go before it ceased to rotate.

Lnewqban

Are you using an air filter in your cars if they are running on dusty tacks?

Bearings are tough, but a mix of oil and fine dust can wear them out soon.
The more loose they become, the faster they become spinning trash.

Any possibility for the crankcase to be deformed by uneven support?

Best luck with the new set of bearings!

cutaway

What fuel are you using, and does it have any castor oil in it?

Its been my personal experience that with a healthy percentage of castor oil, slightly rich needle settings, engines can be used for decades before bearings will fail due to wearing out (assuming they weren't junk bearings to begin with). The most common failure modes seem to be rust and ball retainer cages grenading at very high RPM's.

Cages grenading can be fixed by using a fully packed race (thus eliminating the cage). Rust is a storage/fuel issue.

pure speed:]

ya i need a new rear bearing.its weird today i had my .18cvr stop dead,tore it down damn rear bearing again its expected tho im at 9+ gallons on this one didnt explode and the piston an sleeve are still like new lol.
Ya only the rear bearing is wobbly no rust,but i have aluminum on my head button and piston i sanded them wit 2000grit fix that but i think the crank is wobbling so bad, the intake port on the crank is chewing the case in the carb throat thus causing further damage??? dont kno 4sure but on the crank theres scuff marks no chunks of aluminum.

pure speed:]

forgot to mention the aluminum dibris was not bad and only by the exhaust port side if it maters?thanks 4 the help

1QwkSport2.5r

I do not care who you are, Bearings do not always last as long as they should. With the huge influx of cheap chinese engines, you oftentimes get cheap chinese bearings. Personally, I'd order a set (replace both bearings even if one is bad - peace of mind goes a long way here) of stainless bearings. Then you dont have to worry much about the bearings rusting. I run all-castor in all of my engines and have zero rust issues. The only engine I have that I replaced the bearings in is my TT .46 Pro because the stockers had metal cages and since I'm winding it up on small props, I wanted phenolic cages in case the retainer falls apart at RPM. RC-Bearings.com is a good place to get bearings from. They sell sets as well as single bearings. They have just about any size you would ever need. Good pricing, fast shipping, good product. Done deal for me.

I havent had to replace bearings on any of my other engines - never needed to. I've always ran fuel with at least 2-4% castor in my car engines, Aero engines were getting a 50/50 mix of syn/castor and now all castor/no synthetic . (I really dislike synthetic oil in glow engines - it just invites rust. Even with after-run oil. ) The ticket when storing an engine to prevent any rust from forming is basically rinse with clean alcohol, let dry, and flood the engine with oil. Dump out the excess and put in a ziplock to stuff in the drawer. That is really the only way to coat all of the surfaces with oil and prevent rust and corrosion from setting in. If you use high amounts of Castor oil, this step probably isnt necessary if you run every last drop of fuel out of it when done for a longer period of time. I use no after-run oil and have zero rust problems. Just a nice film of polymerized castor.

pure speed:]

when i store an engine i completly disasemable the motor and clean all parts with isopropel alcohol and a clean rag. i use an air compresser to blow off every inch spotless including the case and bearings, than use a mix of aro and airtool oil to lube the BB.

1QwkSport2.5r

You shouldnt pull the piston and sleeve out of a running engine unless there is something wrong with it. The piston and sleeve fit is altered slightly during disassembly and usually requires a sort of "re-break-in" to get the piston to re-seat itself...... I was chewed a new one when I talked about tearing an engine down just to look inside of it, so I'm just passing on the advice that was passed on to me - I'm just being nicer about it.. LoL..

Kweasel

My Feedback: (29)

Corrosion may not look like rust. Under a microscope you will see chemical pitting that you can hear and feel, over time they get loose. The same bearing in a gasoline burning engine will not have nearly as much of this problem. Dirt will ruin the piston fit a lot faster than the bearing so use good filters. Flush the engine before you put it away. Cheap spray oil or whatever will go a long way toward preserving the steel parts.

DarZeelon

Quote:

ORIGINAL: 378

They should last the life of the engine. ESPECIALLY in an OS...

Quote:

ORIGINAL: 378

...They should last the life of the engine. If the bearings, in an OS especially but even in a junk engine, are going out after just three gallons, there's something else wrong.

This is quite a naïve claim, you're making here...

If there is an engine make, which seems to be notorious for puking its bearings; at least from the frequency bearing replacement threads that are opened for it in RCU; it is OS and no other.

OS use NTN bearings for many of their engines. Maybe it is the wrong choice...



Many bearing problems are actually ... owner problems.

If engines are run dry at the end of each flying session (andafter-run oil is used afterward); and if fuels that contain a substantial percentage of castor oil are used, the bearings' lives will be prolonged...

Failure to do so is definitely an 'owner problem'; not an engine problem.


I always do so and have never had to replace the bearings, in any engine I ever owned.


EDIT: Wording.

pure speed:]

Could be that i got the motor from a very nice fellow RCU member "Jackripped" that has converted to Brushless.Anywho the engine didnt run,and sat on a shelf for a year but was mint. opon disasembly ive noticed a very small amount of what looked to me as castor stains on the rear crank bearing.I'm just gonna have to get a new rear BB,debating on what brand o.s. BB's are 22$ apice and are not ceramic or stainless, i dont think? My question is do you guys think i would be wiser to get acer or boca ceramics or...

BarracudaHockey

My Feedback: (11)

Wow, if only that were even partially true.

Hobbsy

My Feedback: (102)

I have a set of Boca ceramic bearings in a Fox .50, they seem to be indestructable so far run both as a glow and Diesel. Short story is that I just don't think about them anymore.

pure speed:]

Thanks Hobbsy! thats just what i wanted to hear.

DarZeelon

Quote:

ORIGINAL: pure speed:]

...I'm just gonna have to get a new rear BB,debating on what brand o.s. BB's are 22$ apice and are not ceramic or stainless...

Pure Speed,


I know Dave Hobbs supports buying bearing from Boca Bearings, on account of them being an advertiser in RCU...

However, Paul McIntosh of RC-Bearings is a participant in this forum and sells [link=http://www.rc-bearings.com/catalog/product_info.php?cPath=30_31&products_id=353]this rear bearing[/link], which has a polyamide cage; like Boca's high-speed set.
He sells it for just a very fair $4.89.

It is the same C3 bearing as Boca's, probably made by the same manufacturer, or an equivalent one...

Compare this to others.

RCER88

My Feedback: (25)

Lean runs are just as hard on bearings as it is on the piston and sleeve. At times trying to get that last minute peak of power out of the engine can lead to premature destruction of your engine. I have glow engines over twenty years old. I have NEVER had to replace bearings and I DO NOT use after run oil. I add two capfuls of castor oil to EVERY gallon of fuel I open. I get slime everywhere but I have good running engines with no corrsion issues. Assembled airplanes are stored nose down so oil left in the engine gets to the bearings. Will they gum up? On occasion sure I put a little WD in them to lubricate and loosen them up and then I run that engine right away to get that synthetic oil out of the engine.

When I first start an engine on that day before the first flight I like to run it sloppy rich for a moment then start leaning it out. That gets the entire engine a chance to get lubricated and wet inside. I run the engine at least two clicks rich and some even more. Airplanes will tend to lean out as the fuel burns out of the tank. I very seldom have "flame outs" because of this policy. I don't care what the experts say. After run oil is NOT needed if castor oil is used. Castor is better at preventing corrosion.

earlwb

Basically it really depends on the brand and model of the engine. The manufacturer may use cheaper bearings in one model and better bearings in another model Some manufacturers use quality bearings and another might use the cheapest bearings they can get. Some brands of engines tend to go a very long time before the bearings need replacing, other brands not so long, and some brands may have bad bearings in a engine before you even fire it up for the first time.

So the bearings may last for years, or be bad right out of the box before you even use the engine.

As mentioned already a number of factors come into play for bearing longevity too.

subbass

My Feedback: (13)

After running the engine alway's disconnect the fuel line and run the engine until it stops firing(you may have to start it a few times until it is completely clear of fuel) and then use after run oil.Make sure the piston is at bdc and use enough oil to form a pool in the crankcase and turn the motor over by hand to spread oil on the rear crankshaft bearing and one more thing never put after run oil through the carb as it can harden the o rings in the carb use the glowplug hole with the piston at bdc so the ports are open and the oil can flow to the rear bearing.Also make sure to do this right after you stop running the engine for the day as rust will start right away.Alway's do this even if you are going to store it even overnight.

blw

My Feedback: (3)

Just keep in mind that WD-40 isn't a lubricant.

I don't think anyone mentioned crashes or prop strikes that shorten bearing life.